Pacemakers – Key Vocabulary

Flashcards covering essential vocabulary related to pacemaker indications, components, functions, coding, and malfunctions.

Pacemaker (Cardiac)

An implanted device that delivers electrical impulses to stimulate heart contractions when intrinsic rhythm is inadequate.

Cardiac Output Formula

Cardiac Output = Heart Rate × Stroke Volume; pacemakers address inadequate heart rate to restore output.

Sick Sinus Syndrome

Disorder in which the SA node malfunctions, often requiring pacemaker support.

Atrioventricular (AV) Conduction Delay

Slowed or blocked impulse conduction through the AV node; common indication for ventricular pacing.

Post-Bypass Surgery Bradycardia

Slow heart rate following cardiac bypass surgery that may necessitate temporary or permanent pacing.

Millivolt / Milliamp (mV / mA)

Units measuring the amplitude of electrical energy delivered by a pacemaker lead to myocardial tissue.

Millisecond (ms)

Unit of time describing the duration of pacemaker stimulus delivery.

Synchronous (Demand) Pacemaker

Device that senses intrinsic cardiac activity and delivers impulses only when natural beats are inadequate.

Asynchronous (Fixed-Rate) Pacemaker

Device that paces continuously at a preset rate regardless of the heart’s own activity.

Pacer Coding – 1st Letter

Indicates the chamber(s) being paced: V (ventricle), A (atrium), or D (dual—both).

Pacer Coding – 2nd Letter

Indicates the chamber(s) being sensed: V, A, or D (dual).

Pacer Coding – 3rd Letter

Indicates pacemaker response to sensing: I (inhibit), T (trigger), or D (dual—both functions).

Capture

Successful depolarization of the cardiac chamber following a pacer spike, producing a contraction.

Sensing

Pacemaker’s ability to detect intrinsic cardiac electrical activity and decide whether to pace.

Failure to Fire

Malfunction in which the generator does not deliver an impulse when needed, often due to battery end-of-life.

Failure to Capture

Impulse is delivered but does not depolarize myocardium; causes include lead fracture or dislodgement.

Failure to Sense

Pacemaker does not properly detect intrinsic beats, resulting in inappropriate pacing activity.

VVI Pacemaker

Single-lead device that paces (V), senses (V), and inhibits (I) in the ventricle; used for AV block.

DDD Pacemaker

Dual-lead device that paces and senses both atrium and ventricle with dual responses (trigger/inhibit).

DVI Pacemaker

Dual-lead system that paces both chambers, senses ventricle only, and inhibits pacing as needed.

Biventricular (BiV) Device

Three-lead system pacing right atrium, right ventricle, and left ventricle via coronary sinus to resynchronize contraction.

Lead (Pacemaker)

Insulated wire that delivers electrical energy from the generator to cardiac tissue and senses activity.

Generator

Implanted power source and computer that controls pacing rate, output, and sensing thresholds.

Pacer Spike

Vertical line on ECG indicating delivery of a pacemaker impulse.

Negative QRS in Paced Rhythm

Appearance of a downward QRS deflection because ventricular stimulation originates from the lead tip upward.

Sinoatrial (SA) Node

Primary cardiac pacemaker whose failure may necessitate atrial or dual-chamber pacing.

Atrioventricular (AV) Node

Conduction relay between atria and ventricles; block here often treated with ventricular pacing.

Purkinje Fibers

Ventricular conduction network that delivers impulses to myocardium and interacts with pacing leads.

Trigger (Pacemaker Response)

Generator action that delivers an impulse when sensed activity is inadequate.

Inhibit (Pacemaker Response)

Generator action that withholds an impulse when sufficient intrinsic activity is sensed.

Capture Threshold

Minimal electrical energy required to consistently depolarize myocardium; determined during implantation.

End-of-Life (EOL) Battery

Stage when generator battery capacity is nearly depleted, risking failure to fire.

Coronary Sinus Lead

Electrode placed in coronary sinus to pace the left ventricle in biventricular devices.